There's nothing wrong with the standard old favorite - the pink eraser! I use this a lot in general pencil sketching. I just don't use this on watercolor paper where I use a magic rub eraser instead. This may not damage that paper, but I'm just cautious with it. For my regular general sketchbook, though, this is my basic eraser of choice.

I cut up Pink Pearl erasers into about five pieces per eraser. These pieces are put out in the plastic bins that are always on the student tables. I have found that this helps slow down the rate at which the erasers are used up and saves money.